Fluid heater support



FLUID HEATER SUPPORT Eiledsept. 16, 1965 7 4 sheds-sheet 1 l www "fiwf 2g Bymml: IH l im fi* il'" N 32 2. lL I' INVENTOR.

ALWIN W. AMBROSE A I AGENT FIG March'. 7, 1967 A. w. AMBROSE 3,307,524

FLUID HEATER SUPPORT Filed sept. 16, 1965 4 Sheets-Sheet 2 INVENTOR.

ALwlN w. AMBRosE BY Er KW?- A ENT March 7, v1967 A. W. AMBROSE FLUID HEATER SUPPORT 4 Sheets-Sheet 5 Filed sept. 16, 1965 INVENTOR.

ALWIN W. AMBROSE BY 3f/f GENT March 7, 1967 A. w. AMBROSE FLUID- HEATER sl-JPPoR'r 4 Sheets-Sheet 4 Filed sept. 16. 19e5- AGENT FLUID HEATER SUPPORT l Alwin W. Ambrose, Hazardville, Conn., assigner to Combustion Engineering, Inc., Windsor,` Conn., al corpora- This invention relates to fluid heaters and particularly to an apparatus for supporting the lower furnace wall tubes of a steam generator from the upper furnace wallv tubes of the steam generator and a unit in which the furnace wall circuit contains a fiuid mixing header system.

All large fossil fuel fired steam generators are of the top supported design. Building steel supported on the ground is erected so that it passes over the steam generator with the upper portion of the steam generator being supported from this building steel. In these steam generators which have vertical furnace wall tubes lining the walls of the furnace the load of the lower portions of the furnace structure including burners, insulation, casing, etc. is carried by these vertical tubes.

In a once-through steam generator as the fluid is passed upwardly through the tubes of the furnace walls, the temperature isincreased due to radiation from the combustion occurring within the furnace. However, due to erratic slag patterns on ythe furnace walls and the distribution of the heat within the furnace, varying amounts of heat are picked up in different tubes. Therefore, the temperature of the fluid leaving the furnace wall tubes varies from tube to tube. This unbalance is magnified by the fact that the specific volume of the fluid increases as it becomes hot with this, in turn, .tending to decrease the flow in that particular tube. With the decreased ow the tube gets even hotter resulting in more increase in specific volume; Although this phenomena generally does not occur to such an extent that the flow in the tube becomes completely unstable, it does operate to magnify the temperature unbalance problem.

Obviously, one of the parameters which determine this unbalance is the amount of heat picked upin a single pass. In order to reduce the unbalances occurring in the furnace wall tubes, mixing header systems have been introduced at a location within the furnace walls. The liuid then leaving the lower section of furnace wall tubes is mixed in this header system'so that it enters the upper section with a greatly decreasedunbalance, thereby decreasing the temperature unbalance at the outlet of the furnace wall.

In order to obtain this mixing the furnace wall tubes must be bent outwardly from the furnace wall and run to a mixing header. Since these furnace walls are structural members carrying vertical loads, a design must be developed to transfer the loading from the upper furnace wall tubes to the llower furnace wall tubes. This has been generally accomplished by intermeshing alternate tubes of the upper and lower section and bringing the tubes out at several different elevations. the inlet and outlet of the furnace wall tubing results in considerable complication of the casing side of the furnace wall structure. In this area there are located on all large steam generators in addition to the insulation a multiplicity of buckstays running both in the horizontal and vertical direction. Since all of these tubes must be brought to a common mixing header system, vertical runs are required outside the furnace and undesirable interference problems are encountered. Furthermore, it is advantageous to place the mixing headers as close to the tubes as possible to avoid interference with vertical buckstays.

A large percentage of the heat absorbed in the furnace is absorbed in the lower portion of the furnace in the This dual location for 3,397,524 Patented Mar. 7, 1967 area of the burners. In order to obtain a good location for the mixing header with respect to the amount of heat picked up, it is desirable to locate this header at a relatively low elevation down almost as far as the burners, if possible. In these areas, however, the heat absorption rate in the furnace walls is quite high. Therefore, structural members which form a portion of the furnace wall cannot be so designed that there is much distance be tween any portion of the finfand the fluid cooled tube to which it is welded. Excessive fin lengths result in high fin metal temperatures due to the heat flowing to the tube and, therefore, very low strengths.

My invention is related to a structural joint of the type described. Adjacent tubes of the lower furnace walls are joined at their upper end by a return bend which lies in the plane of the wall. A single outlet from the return bend is angularly displaced from the plane of the wall so thatrit carries the uid from the lower furnace wall tubes outwardly to the mixing header system. vThe lower end of the upper furnace wall tubes are similarly formed with an inlet to the upper pairs of tubes being angularly displaced from the plane of the wall and being supplied from the mixing header system. The fin space between the tubes may be kept to a minimum byselecting alternate .pairs of tubes from the upper and lower furnace walls whereby the crowns of the return bends are alternately located. Furthermore, the angularly displaced outlets and inlets may be displaced from the plane of the wall only a sufficient amount to clear the juxtaposed return bends so that the angularly displaced section cuts through a considerable portion of the heavy finned area between return bends cooling and maintaining this fin section at a desirable minimum.

It is an object of my invention to provide a simplified inexpensive arrangement for conveying fluid to and from the mixing header system at a location intermediate a furnace wall pass wherein the tubes forming the lower furnace wall are supported from the tubes forming the upper furnace wall.

It is a further object to provide such e. tubing arrangement such that finning between the tubes forming the support is maintained at the minimum value so the chances of such finning becoming overheated are reduced.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds. k

With these objects in view, the invention comprises an arrangement, construction and combination of the elements of tlie inventive organization in such a manner as to attain the results desired. Such is hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, which is shown by the accompanying drawings wherein:

FIG. 1 is a side elevation of a steam generator showing the general method of support;

FIG. 2 is a side elevation of a detail of the support arrangement where the furnace wall tubes are 1% inch diameter with the upper and lower return bends being generally tangent while the outlet and inlet legs are at an angle of 45 and formed of ll/z inch tubing;

FIG. 3 is a front elevation of the detail of FIG. 2;

FIG. 4 is a side elevation showing a detail of the support arrangement wherein the furnace wall tubes are 1% inch diameter with the outlet and inlet legs being at an angle of 45 and formed of 11/2 inch tubing and where the juxtaposed return bends are separated by a distance about equal to one half the width of the fins between adjacent tubes;

FIG. 5 is a front elevation of the detail of FIG. 4;

FIG. 6 is a side elevation showing a detail of the support arrangement using 1% inch tubes onthe furnace walls with 1% inch inlets and outlets and with the outlets and inlets being displaced from the plane of the wall only a suflicient amount to avoid interference with the opposing return bends; and

FIG. 7 is a front elevation of a detail of FIG. 6.

In the illustration of FIG. 1 fuel is introduced through burners 12 into the yfurnace 13 where combustion takes place with the combustion products passing outwardly through the flue 14. Feedwater to the steam generator passes from lthe economizer (not shown) to the furnace wall inlet headers 15. It passes upwardly through tubes 16 lining the walls of the furnace 13. These tubes are 1% inches outside diameter and have a Web 18 which is 1A inch thick and 1/2 inch wide located intermediate adjacent tubes and welded to these adjacent tubes.

The tubes of the lower furnace wall section 19 convey the fluid upwardly to the mixing header elevation which is described in more detail hereinafter. Fluid from this 'mixing header system is then conveyed through the tubes forming the upper portion of the furnace tubes 20 through the furnace wall outlet header 22. The steam passes from this furnace wall outlet header 22 through the superheaters (not shown) and then to a steam turbine (not shown) for the generation of electric power.

Building steel verticals 27 support building steel horizontals 28 from which the steam generator is supported. Tie rods 29 support the upper furnace walls through lugs 30l from the horizontal building steel 28. These lugs 30 are securely welded to the furnace wall tubes 20 with the weight of the steam generator structure then being carried by these tubes.

The furnace structure is stayed to prevent distortion due to internal furnace pressures by a buckstay framing system. This system comprises small horizontal buckstays 32 which pass transversely to the tubes and resist outward pressure. Forces from these small horizontal buckstays 32 are transmitted to vertical buckstays 33 with a force, in turn, being supported to horizontal buckstay trusses 34. The large trusses on opposite sides of the furnace are structurally tied together so that forces against each truss are opposed by forces against the other trusses.

FIGS. 2 and 3 show a detail of the furnace wall arrangement in the area of the mixing header system. The lower furnace wall tubes 19 are 1% inch tubes on 1% inch spacing with 1/2 inch wide webs 18 being welded intermediate the adjacent tubes. The upper furnace wall tubes 20 are similarly sized and disposed. At the upper end of the lower furnace wall tubes 19 a return bend 37 is located. This return bend is most simply formed as a uniform radius bend and is so illustrated. However, a forged return bend of a more angular nature could equally well be used. Outlet tube 38 passes from the return bend 37 and is displaced at an angle of 45 from the plane of the wall, this angle being selected in the interest of uniformity and simplicity. This outlet tube conveys fluid to the upper header 39 of the mixing header system.

Fluid from the upper mixing header is conveyed through the crossover pipe 40 to the lower header of the mixing header system 42 from which it is supplied to the upper furnace wall tubes 20.

The lower portion of the upper furnace wall tubes 20 are treated in a manner similar to the upper ends of the lower furnace wall tubes 19 with adjacent tubes being joined by return bends 43. Inlet tube 44 similarly displaced 45" from the plane of the wall supplies the mixed Huid from the lower header 41 to the upper tubes 20 through the return bend 43. With this arrangement the inlet and outlet tubes may extend directly to the headers without bending.' In addition to inexpensive construction this permits the headers to be located close to the wall. Since these long horizontal headers 39 and 42 are located inside the vertical buckstays 33, this permits the vertical buckstays to be located close to the furnace wall, minimizing the extensions which must be supplied to join the horizontal buckstays 32 to the vertical buckstays 33. The tubes are arranged so that they are both veritable and drainable to the header system. Accordingly, corrosion problems duefv'fto Water pockets and tube blockage problems due to air blockage are prevented.

Outlet tube 3S is of 11/2 inch diameter contrasted to 1% inch diameter of the lower furnace wall tubes 19. This tube, however, has to carry the flow egressing from two of the `lower furnace wall tubes and, accordingly, an increased diameter of this tube aids the stability of the furnace wall section. Since the spacing of the wall tubes 19 is 1% inches, the outside diameter of the outlet tube 38 and the inlet tube 44 should not exceed this. So limited the tubes 38 and 44 may pass one another without offsetting, while a slightly smaller diameter allows tolerance to facilitate construction.

The welded fin 18 which is located intermediate adjacent tubes of the upper and lower furnace sections is continued through the area of the support junction filling the space between adjacent return bends. In order to reduce the size of the fin at this joint, alternate tubes are selected from the upper and lower section so that the return bends of these sections nest together. However, there still will be substantial fin area just above the crown of the return bends if the return bends were all that were being considered. The 45 outlet 38 and the 45 inlet 44, however, cut through the plane of the n at this critical location thereby decreasing the size of the fin and further cooling the fin adjacent thereto. The front face of the fin 18 is located on the centerline of the tube so that the fin tends to be maintained at a location relatively remote from the furnace. The amount of n cooling obtained at this remote location is more substantial than it would be had the fin been located on or in front of the tube centerline, since the tube cuts through a larger portion of the fin.

FIGS. 4 and 5 show a detail of the furnace wall arrangement n the area of the mixing header system with an increased spacing between the juxtaposed return bends. Return bends 37 and 43 are spaced with a distance between these bends which is generally equal to one half the width of the web 18 rather than being generally tangent. Such spacing permits increased welding access and facilitates the construction of a dependable structural joint where all welding can be done in an area which is generally along the tube centerline. This avoids eccentric loading in portions of the tube which may be encountered Where the return bends are tangent.

FIGS. 6 and 7 show a detail of a furnace wall arrangement in the area of the mixing header system which minimizes the finned area. Lower furnace Wall tubes 19 are again 1% inches outside diameter with the outlet tube 58 also being 1% inches outside diameter. This outlet leg 58 is angularly displaced from the plane of the furnace wall a minimum amount, with this amount being just sufficient for the outlet tube 58 egressing from return bend 37 to clear the return bends 43. Such a positioning of this outlet leg permits the tube to cut through the web 18 to the maximum amount and, accordingly, increases the cooling effect that this leg as on the welded web 18. Inlet leg 64 carrying fluid to the return bend 43 is similarly angularly displaced from the plane of the furnace wall a minimum amount with this amount being selected so that the inlet tube 64 is generally tangentin passing by the rear edges of the return -bend 37. In this embodiment the return bends 43 and 37 are spaced from one another a distance approximately equal to one half the web thickness to permit sucient welding access to obtain a good structural joint.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made Etherein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within. the. purview of. my invention.

. What I claim is: 1. In a liuid heater having a furnace, generally vertical tubes including a lower section and an upper section lin- `fluidly joining upper ends of 4pairs of adjacent tubes of said lower section with said return bends being in the plane of the furnace wall tubes; a tube comprisinga single outlet from said first return bend angularly displaced from the plane of the furnace wall tubes and cx' tending outwardly from said furnace to said mixing header system; second return bends in the plane of the furnace wall tubes fluidly joining the lower ends of pairs of adjacent tubes of said upper section; corresponding tubes of the upper and lower sections being in line, and the joined pairs of adjacent tubes being selected so that the return bends are staggered with the lower return bend crown nesting between adjacent upper return bends; a

tube comprising a single inlet to said second return bendv angularly displaced from the plane of the furnace wall tubing and extending outwardly from said furnace to said mixing header system; gas tight sealing means intermediate the first and second return bends, with said sealing means being in the plane of the. furnace wall tubes and having a portion extending through a generally triangular area between the nesting return bends; and'said tubes comprising single inlets and single outlets connected to their corresponding return bends at the crown of the bend, said tubes having a portion extending on the furnace side of the scaling means in the generally triangular area.

2. An apparatus as in claim 1 wherein the tubes coniprising a single outlet and the tubes comprising a single inlet are each displaced from the plane of thev furnace wall tubes by an angle of 45.

3. In ,a fluid heater having a furnace, generally ver' tical tubes including a lower section and an upper section lining the wallsvof said furnace, a mixing header system receiving uid froms'aid lower section and dis# charging the mixed fluid to the upper section, with -said lower section being supported from said upper section, an improved junctionv arrangement comprising: a first return bend fluidly joining upper ends of pairs of adjacent tubes of said lower section with saidretu'rn bends being in the plane of the furnace wall tubes; a tube comprising a single outlet from said first return bend angularly displaced from the plane of the furnace wall tubes and extending outwardly from said furnace to said mixing header system; second return bends in the plane of the furnace wall tubes uidly joining the lower ends of pairs of adjacent tubes of said upper section;

`corresponding tubes of the u-pper and lower sections being in line, and the joined pairs of adjacent tubes being selected vso thatthe return bends are staggered with the lower return bend crown nesting between adjacent upper return bends; a tube comprising a single inlet to said second return ben-d angularly displaced from the plane of the furnace wall tubing and extending outwardly from said furnace to said mixing header system said tube comprising a single outlet from ysaid first return bend angularly displaced from the plane of the furnace wall tubes by an angle of less than l90" so that this tube joins the mixing header system at an upper elevation; lsailgtube comprising a single inlet to said second return bend angularly displaced from the plane of the vfurnace wall tubes by an angleof lessthan with this tube joining the mixing header system at a lower elevation, whereby the mixing header system and tubing arrangement is both drainable and venltable.

4. In a iiuid heater having a furnace, generally vertical tubes including a lower section and an upper sec tion lining the walls of said furnace, welded webs intermediate adjacent tubes, a mixing header system receiving .uid from said lower section and discharging the mixed iiuid to the upper sec-tion, with said lower section being supported from said upper section, an irnproved junction arrangementcomprising: a first return' bend iiuidly joining upper lends of pairs of adjacent tubes of said lower section with said return bends 4being in the plane of the furnace wall tubes; a tube comprising a single outlet from said first return bend of a diameter less than the spacing of the generally vertical tubes angularly displaced from the plane of the furnace wall tubes, and extending outwardly from said furnace to said mixing header system; second return bends in the plane of the furnace wall tubes iiuidly joining the lower ends of pairs of adjacent tubes of said upper wall section; corresponding tubes of the upper and lower sections being in line, and the joined pairs of adjacent tubes being selected so that the return bends are staggered with the lower return bend crown nesting between adjacent upper return bends; a tube comprising a single inlet to said second return bend of a diameter less than the spacing of the generally vertical tubes angularly displaced from the plane of the furnace wall tubing and extending outwardly from said furnace to said mixing header system; and means for carrying the weight of the lower furnace section from said upper furnace section.

5. An apparatus as in claim 4 having also a welded seal connecting the nesting return bends, being in the plane of the furnace wall, and being a continuation of said welded webs; with said 'welded seal having a Width between the nested return bends at least one-half the welded web width between adjacent vertical tubes.

6. An apparatus as in claim S wherein the tubes comprising single inlets and single outlets for a portion extending on the furnace side of said welded seal where by the size of the welded seal is reduced and the cooling of the welded seal is increased.

7. An apparatus as in claim 6 wherein the tube comprising a single outlet from said first return bend passes generally tangent to the tubing of the second return bends; said tube comprising a single inlet to said second return bend passes generally tangent to said first return bends, whereby the cooling of said welded sealing means is maximized. 8. An apparatus as in claim 6 wherein the welded webs intermediate adjacent tubes and the welded sealing means are located so that the front face of the web and sealing means are on the centerline of the furnace wall tubes.

References Cited by the Examiner UNITED STATES PATENTS KENNETH wf SriMGUE. Primary Examiner. 

1. IN A FLUID HEATER HAVING A FURNANCE, GENERALLY VERTICAL TUBES INCLUDING A LOWER SECTION AND AN UPPER SECTION LINING THE WALLS OF SAID FURNANCE, A MIXING HEADER SYSTEM RECEIVING FLUID FROM SAID LOWER SECTION AND DISCHARGING THE MIXED FLUID TO THE UPPER SECTION, WITH SAID LOWER SECTION BEING SUPPORTED FROM SAID UPPER SECTION, AN IMPROVED JUNCTION ARRANGEMENT COMPRISING: A FIRST RETURN BEND FLUIDLY JOINING UPPER ENDS OF PAIRS OF ADJACENT TUBES OF SAID LOWER SECTION WITH SAID RETURN BENDS BEING IN THE PLANE OF THE FURNANCE WALL TUBES; A TUBE COMPRISING A SINGLE OUTLET FROM SAID FIRST RETURN BEND ANGULARLY DISPLACED FROM THE PLANE OF THE FURNANCE WALL TUBES AND EXTENDING OUTWARDLY FROM SAID FURNANCE TO SAID MIXING HEADER SYSTEM; SECOND RETURN BENDS IN THE PLANE OF THE FURNACE WALL TUBES FLUIDLY JOINING THE LOWER ENDS OF PAIRS OF ADJACENT TUBES OF SAID UPPER SECTION; CORRESPONDING TUBES OF THE UPPER AND LOWER SECTIONS BEING IN LINE, AND THE JOINED PAIRS OF ADJACENT TUBES BEING SELECTED SO THAT THE RETURN BENDS ARE STAGGERED WITH THE LOWER RETURN BEND CROWN NESTING BETWEEN ADJACENT UPPER RETURN BENDS; A TUBE COMPRISING A SINGLE INLET TO SAID SECOND RETURN BEND ANGULARLY DISPLACED FROM THE PLANE OF THE FURNANCE WALL TUBING AND EXTENDING OUTWARDLY FROM SAID FURNACE TO SAID MIXING HEADER SYSTEM; GAS TIGHT SEALING MEANS INTERMEDIATE THE FIRST AND SECOND RETURN BENDS, WITH SAID SEALING MEANS BEING IN THE PLANE OF THE FURNANCE WALL TUBES AND HAVING A PORTION EXTENDING THROUGH A GENERALLY TRIANGULAR AREA BETWEEN THE NESTING RETUN BENDS; AND SAID TUBES COMPRISING SINGLE INLETS AND SINGLE OUTLETS CONNECTED TO THEIR CORRESPONDING RETURN BENDS AT THE CROWN OF THE BEND, SAID TUBES HAVING A PORTION EXTENDING ON THE FURNACE SIDE OF THE SEALING MEANS IN THE GENERALLY TRIANGULAR AREA. 